Metering device



Nov. I26, 1946.

F. LE G. BRYANT METERING DEVICE:

Filed naa-y 25. 1942 3 Sheets-Sheet 1 Iii - INVENTOR ATTORNEY Nov. 26,1946. |:l E G, BRYANT 2,411,613

METERING DEVICE Filed May 25, 1942 3 Sheets-Sheet 2 l INVENTOR 7* WX Mx267mb! '1 BY I ATTORNEYS I Nov. 26, 1946. F. E G. BRYANT METERING DEVICEFiled May 25, 1942 3 Sheets-Sheet 3 figg y lNvENToR M1122 @uw BY ya fdATTORNEYS QNX , www

Paten-ted Nov. 26,1946

Nr oi-'rlcls Maremma nevica Forrest Le GrandBryant, NewYork,

signor to Jemen VMa Bloomfield,

chinery Company, N. a corporation of New i apuestan Mey z5, 1942, semiNo. 444,351

d Claims. (Cl. 'I3-231) This invention relates to the art of meteringthe flow of fluids or other i-lowable material and has for its objectthe provision of a simple and accurate apparatus for measuring suchilow.

An additional object is the provision of an apparatus which ofl'er verylittle restriction to the flow.

Another object is the provision oi an apparatus which may be easilydisassembled for cleaning.

A further object of this invention is a metering device of simplestructure which may be easily taken apart for cleaning and which meetsall the requirements promulgated by the boards .of health with respectto apparatus used in the handling of food products.

Another object of this invention is a metering device having provisionto effect compensation for change in the specific gravity of the liquidbeing metered due to temperature variation in the liquid during themetering operation.

' A still further object of the invention is a metering device in whichthe number of rotations of a metering member is registered through theintermediary of variations in light intensity effected by rotation ofthe metering member.

In a preferred embodiment ofthe invention, liquid or other material tobe metered is passed through a light-transmitting tube wherein it causesa movably mounted member to rotate at a speed proportional to the rateof flow. The rotational member is arranged to be interceptive of a lightbeam and causes the beam to be interrupted in such a manner as to causea state of high illumination in one part of the liquid and a relativelylow state o f illumination in another part of the liquid or an almostcomplete interruption of the beam or a reflection or refraction thereof.The rotation of the member causes a succession of periods when arelatively high or relatively low state of illumination exists or asuccession of interruptions or reflections or refractions of the lightbeam. The interrupted beams of light or the succession of highilluminations, reflections or refractions are supplied to aphoto-electric cell, thereby causing such cell to becomecapable ofconducting current proportional to or approximately proportional to thestate of illumination. Thus, the number of rotations of the member isimpressed on the photo-electric cell as periods of increasedconductivity of such cell, and usually there are two periods for eachcomplete revolution of the member. Electrically actuated counting meansare controlled by the photo-electric cell in respense to the variationin the intensity of :uumlnation so that the counting means registers thevolume of material flowing through the tube in a given time. I

. One field of use for the metering device isin the measurement of theflow of milk or other similar liquid. Certain characteristics of theapparatus are definitely advantageous to the measurement'of milk flow,particularly since the transmission factor of milk for the passage oflight is relatively low. Therefore, for milkmetering apparatus, thephoto-electric cell is mounted in close proximity to thelight-transmitting tube and in relatively close proximity to the pointoi contact of the light beam with the light-transmitting tube. Therotating member preferably is of spiral form mounted on bearings withits rotational axis intersecting the light beam axis and lying in aplane with the axis of the photo-electric cell and divides the column ofliquid into two equal parts. During that portion of the rotation of saidmember that one edge is in the arc between the light beam axis and theplane of its rotational axis and the photoelectric cell axis, a st ateof low illumination exists in that portion of the column oi liquid whichsupplies light to the photo-electric cell, while a high state oiillumination exists in the remainder.of the liquid column. After theedge of the rotating member has left the end of said arc. a state ofhigh illumination exists in that portion 'of the column oi liquid whichsupplies light to the photo-electric cell'until the remaining edge ofsaid member passes across the light beam axis. This, of course, occurstwice for each revolution of the member. With this arrangement,advantage is taken of the light which is reflected from the solidsand/or fat in the milk and each time such light is reflected from themilk, the photo-electric cell is placed in a state of relatively highconductivity for the purpose of actuating the indicating or countingmeans. In the case of relatively transparent liquid such, for example,as beer, a beam of light may be directed straight or nearly straightthrough the liquid, in which case, the photoelectric cell would bemounted on one side of the light-transmitting tube and the light beamwould enter the light-transmitting tube at a point less adjacent to thephoto-electric cell and possibly.

effective light rays for use with milk are the infra-red rays. For thisreason, a high wattage tungsten filament lamp preferably is used as thesource as when using the total light. This has advantage in the case ofvoltage drop since the decrease in total light would be approximatelyinversely proportional to the third power of the `drop in voltage wherethe decrease in infra-red radiation would be inversely proportional toapproximately one-half one power of the drop in voltage.

It has been found when measuring milk with the measuring device of thisinvention, that under certain conditions, an extreme variation occurs inthe light transmission factor of the milk due to varying percentage inits butter fat content. In the case of milk pumped from a large tank inwhich stratification of the cream has taken place, the milk from thelower part of the tank and passing through the device rst may contain 1or 2% butter fat and have a relatively high light-transmission factor,whereas milk that was originally in the top part of the tank and whichpasses through the measuring device later may have a butter fat contentas high as 10% and consequently a much lower light-transmission factor.It is therefore necessary to provide means for highly amplifying thesignals from the photo-electric cell in the case of high butter fatcontent and relatively low light transmission fac-I tor and, to'providethat the amplification will be automatically reduced in the case of lowbutter fat content and relatively high light-transmission factor.

Preferably, the counter is calibrated to register the amount ofl liquidmetered in weight units rather than in volume units and, therefore,variation in the speciilc gravity of the liquid being pumped must betaken into consideration. For this reason, means are provided connectedin such a manner that electrical adjustment may be made eitherautomatically or manually so that the count registered on the countermay bear any desired relation to the number of revolutions of therotatable member.

Other objects, novel features and advantages of this invention willbecome apparent from the following specification and accompanyingdrawings, wherein:

Fig. 1 illustrates partly in section and partly in elevation themechanical portion of an apparatus embodying the invention;

Fig. 2 is a plan view of Fig. 1;

Figs. 3 and i together are a wiring diagram of the electrical portion,and

Fig. 5 is a further modification. Y

In the embodiment disclosed in Figs. 1 to 4, a metal bracket I isprovided with two spaced alined tubular portions and I2 which areprovided with exterior threads. A glass tubev |3' coated with opaquematerial is'interposed between the adjacent ends of the tubular portionsand I2 and is held in placeby nuts |4 with suitable packing I providedto form fluid-tight joints. The tube I3' is equipped with windows |3aand |3b and within said tube is provided a member I6' consisting of aspirally twisted metal ribbon provided at its opposite ends with axialstuds I'I. The axial studs I1 cooperate with pins I8 carried by spidersI9 to rotatably support the member I6. Each spider I9 snugly fits thetubular portion in which it is arranged and is removable therefrom,while the bottom spider rests upon an annular flange 20 provided in thetubular portion |2, the ange serving to locate the member I6' in properrelation to the windows |3a and |3b of tube I3. Passage of a stream ofliquid or a stream of small solids through the tube I3' effects rotationof the member I6.

The bracket I0 is provided with a platform on which is supported a lightsource 22 in combination with a condenser lens 23 for directing a beamof light to the window I3a of the tube I3. Also, the table 2| supports aphoto-electric cell 24' so arranged as to have its cathode facing thewindow |3b of the tube I3". A toothed disk I|0, rotated by a motor III,is arranged to modulate the light beam to audio frequency range of about'100 c'ycles per second. Electrical renergy for the light source 22' andthe motor is supplied from a power circuit L through conductors ||2.Preferably, a casing (not shown) is provided for enclosing the lightsource 22 and photo-electric cell 24 to exclude extraneous light fromthe photo-electric cell and make it responsive only to light from thesource 22.

A transformer has its primary ||3a bridged across the power line' L andis provided with several secondaries ||3b, ||3c, ||3d, ||3e,respectively. A conventional full wave rectifier ||4 has its two anodesI Ill connected to opposite terminals of the secondary I|3c, themidpoint of which is grounded at IIB and has its cathode ||1 bridgedacross the secondary ||3d. The cathode |I1 is connected through aninductance ||8 to one terminal of a potential divider IIB from variouspoints of which lead conductors |20, |2I, |22, |23, |24, |25, with thelast ve leading through inductances |2I, |22', |23', |24', |25', andconductor |26.

A second full wave rectifier |21 has its two anodes |23 connected toopposite ends of the secondary ||3b and has its cathode |29 grounded at|30. The center point of the secondary ||3b is connected by conductor|3| to ground through a relay coil |32 and resistance |33 and a groundedcondenser |3|a is connected to the conductor |3| ahead of the relay coil|32. The nxed'contact |34 of the relay is connected by conductor |35 toone side of the power line L and the movable contact |36 of the relay isconnected through conductor |31 to one terminal of a transformer primary|38a, the other terminal of which is connected through conductor |39 tothe remaining side of the power line L.

The conductor |24 leads to the anode of the photo-electric cell 24 whilethe conductor |23 leads through the cathode heater of the rectifier |21and resistances |40 and |40' to the cathode of the photo-,electric cell24'. A grounded condenser |24a is connected to the conductor |24 and agrounded condenser |26a is connected between the resistances |40 and|402 y A pentode voltage amplifier electron discharge device |4| isconnected to photo-electric cell circuit as an impedance transformer.The cathode of the photo-electric cel1 24 is connected throughconductors |23 and |26 to the control electrode of |4| while the anodeof |4| is connected to the conductor |24. The suppressor electrode andcathode of |4| are connected together and are grounded through theresistance |4|' and the screenL electrode of |4| is connected to theconductor |25 to which is connected a grounded condenser I25a.

The cathode andsuppressor electrode of |4| are connected through acondenser |42 to the control electrode of a pentode voltage amplifierelectron discharge device |48. The` anode of |48 is connected to theconductor |28 to which is connected a grounded condenser |28a, throughinductance |44, across which is bridged a condenser |45 to form a tunedcircuit. The suppressor electrode and the cathode of |48 are connectedthrough resistance |48 to ground. The screen electrode of |48 isconnected to conductor |28 to which is connected agrounded condenser|28a. 'I'he heaters for |4| and |48 are supplied with energizing currentthrough thel conductor |28 and branch conductor |28a.

I'he anodeof |48 is connected through a condenser |41 to the controlelectrode of a beam power amplifier electron discharge device |48 andsaid control electrode is connected to ground through a resistance |48.The anode of '|48 is connected to conductor |2| to which is connectedgrounded condenser |2|a, through transformer primary |58a which isbridged by the condenser |8| to form a tuned circuit. The screenelectrode of |48 is connected to the conductor |22 to which is connecteda grounded condenser 22a.

The terminals of the transformer secondary |881) are connected to theanodes |58 of the fullv wave rectifier |54 and the midpoint oftransformer secondary |58b is connected through a condenser |55 andresistance |58 to the cathode |51 of |54. A pair of resistances |58 and|58 are bridged across the condenser |85, the positive terminal of whichis grounded at |88. A con- -ductor |8| leads from the connection betweenrev sistances |58 and |58 through a resistance |82 to the controlelectrode of |48.

'I'he negative terminal oi' condenser |55 is connected through conductor88 and equal resistances |84 and |85 respectively to the controlelectrodes of gas-filled tetrodes 88 and |81, the cathodes and shieldelectrodes of which are grounded respectively at |88 and 88. Oneterminal of the transformer secondary |58b is connected through theconductor |18 and condensers |1| and |12 respectively to the controlelectrodes of the tetrodes |88 and |81. The anodes of |88 and |81 areconnected through resistances 18 and |14 to opposite terminals of thetransformer secondary |8811.

'I'he heaters for the cathodes of |54, |88 and |81 are furnished withcurrent from the transformer secondary |8e by conductors |18 and |88.

A conductor |88 leads from the connection between the coil |82 and theresistance |88 to the blade 88a of a single blade single-throw switch,the contact of which is connected to conductor |88b. The center point ofthe transformer secondary |88b (the midpoint oi' the transformersecondary |8811) is grounded at |88c through a resistance |88d and aswitch |88e and also is ccnnected through conductor |84 to the blade 84aof a single blade two-throw switch having twol contacts, one of which isconnected to the conductor |88b and the other of which is connected toone terminal of the operating coil |85 of a lio-point rotary switchhaving two banks of contacts |88 and |81 and wipers |88 and |88respectively i'or said banks, the remaining terminal of the coil |85being connected to ground through the resistance |88. The resistance |88is bridged by a condenser |8| and a circuit including a stationarycontact |82 and a movable contact 88, the former of which normallyengages the latter but is caused to move out of engagement therewithupon flow of current through the coil |85.

Preferably, the blades |88a and |84a are interconnected for simultaneousmovement so that the blade |88a closes the circuit between conductors|88 and |88b only when the blade |8411 engages the contact connected tothe coil |85.

The ilrst 36 contacts of the bank |88 are divided into 8 groups of fourcontacts each and the alternate groups are connected to conductors |15and |18 in such manner that one set oi' groups A secondary rotary switchhas an operating coil |85, one end of which is grounded at |88. Thisswitch has a single bank of contacts |81 and a wiper |88 which isgrounded at 88. The first 12 contacts |81 are alternately connected to afirst conductor 11 and a second conductor |18 and contacts I8 to 25 areconnected to the first conductor while contacts 28 to 85 are alternatelyconnected to the two conductors andthe remaining contacts are connectedto the second conductor. nected respectively to conductors |11 and |18.

A transformer primary 28811 is bridged across the transformer -primary|88a by conductors 28| and 282. The transformer secondary 28812 has itsterminals connected to the anodes of ygas-filled tetrodes 288 and 284,the suppressor electrodes and cathodes of which are grounded at 285 and288 respectively. The control electrodes of tetrodes 288 and 284 areconnected through the resistances 281 and 288 and conductor .288 to therotary sistance 2 8 to conductor |8817.

A second transformer primary 2||a isv bridged across the transformerprimary 88a by conductors 28| and 282. The opposite terminals oi thetransformer secondary 2||b are connected lto the anodes of gas-lledtetrodes 2|2 and 2| 8 respectively, the suppressor grids and cathodes ofwhich are grounded respectively at 2|4 and 2|8. The control electrodesof2|2 and 2|8 are connected respectively through resistances 2|8 and 2|1to the rotary switch wiper |88 and through resistance 2|8 to conductor|88b. The midpoint of transformer secondary 2| |b is connected throughresistance 2 8 to the second switch actuating coil |85. The laments of288, 284, 2| 2 and 2|8 are ysupplied with current from transformersecondary ||8e through conductors |18 and |88.

The midpoint oftransformer secondary 288b is connected through conductor228 and resistance 22| to the blade of a single blade double-throwswitch 222 having two contacts 228 and 224'. A conductor 228 leads fromthe contact 224 to one terminal of the actuating coil 228 of a magneticcounter and the remaining terminal of said coil is grounded. The contact228 is connected through conductor 221 to the wiper 2280i a rotaryswitch having two banks oi' contacts 228 and 288. The wiper 228 isadvanced by a stepping coil (not shown) but similar to the steppingcoils |85 and |85 for the wipers |88 and |88 of the two previouslydescribed rotary switches. The wiper 228 is of such construction thatone arm engages only the contacts of the bank 228 and the other armengages only the contacts of the bank 288. and is advanced one step foreach impulse flowing The conductors |15 and |18 are con-y through theconductor 220 in the usual manner for switches 'pf this type. Thecontacts of the two banks 223 and 230 are progressively connected tocontacts supported by a panel 23| of insulating material, al1 of whichpanel contacts except four are in turn connected to a bus bar 232 havingone end connected through the conductor 233 to one terminal of theactuating coil 228 of the counter 228'. (Inorder to avoid a confusingmultiplicity of lines. only four switch contacts are shown as connectedto panel contacts, but it is to be understood that all of the switchcontacts are connected to panel contacts.) The four panel contacts abovementioned as not being connected to the bus bar are connected tocontacts 234 and a wiper 235 is provided to engage the contacts 234successively so as to be in engagement with one to four of saidcontacts, depending upon the position of the wiper. A conductor 235leads from the wiper 235 to the conductor 233. The wiper 235 is actuatedby a thermostat 231 having its bulb 233 arranged in the liquid stream.By propel` manipulation of the switch 222, the midpoint of thetransformer secondary 200|) can be connected to the operating coil 226either through merely the resistance 22| or through the resistance 22|,rotary' switch and panel contacts.

In the operation of the device, the light transmitted through the tubeI3' to the photo-electric cell 24' is dependent upon the position of therotor IB' which is rotated by dow of liquid through the tube I3'. Thephoto-electric cell is subjected to maximum and minimum illuminationonce for each half revolution of the rotor I8'. The current flowing fromthe anode to the cathode of photoelectric cell 24' fiuctuates as theillumination changes. The output of the photo-electric cell has analternating current component of the Asame frequency as the lightinterruption produced by the wheel I I0.

`The rectier |21 supplies a negative potential to the conductor |83 andenergizes the coil |32 to move the contact |36 into engagement with thecontact |34 after the filament of rectifier tube I |4 and the cathode of|21 have successively been heated to emitting temperature.

Positive potential is supplied to the anode of the photo-electric cell24' through conductor |24 while the cathode of 24 is connected throughconductor |26 and resistances |40' and |40 to the least positiveterminal of the voltage divider I I3. Constant positive potential isimpressed on the anode of I4| through conductor |24 and on the screenelectrode of I4| through conductor |25. A posi-- tive bias is suppliedto the control electrode of |4| 'through the conductor |28' by theresistances |40' and |40.

'I jhe alternating current component oi' the photo-electric cell currentiiows through a circuit consisting of grounded condenser |24a, conductor|24, photo-electric cell 24', conductor |26, re

sistance |40' and grounded condenser I25a. Thus, there is acrossresistance I 40' a potential that has an alternating current componentof a frequency controlled by the toothed disk I0 and modulated by themember I8'. This alternating current potential is amplified by thethree-stage amplifier consisting of the electron discharge Vdevices I4|,|43 and |48. The alternating current component of the voltage across theresistance |40' appears across resistance I4 I which is only a smalliraction (l/iooo) of resistance |40' thereby making it possible for theconductor |42a to be considerably l lengthened to permit separation ofthe ampliiler |4l, tube I3', photo-electric cell 24', lens 23', mo

tor |I|, and light source 22' from the other` parts of the mechanism.Also, it eliminates possible instability in electron discharge device|43 which might develop if the high resistance |40' were connecteddirectly into the grid circuit of |43.

The voltage across resistance |4|' is impressed through the conductor|42a on the control grid of |43 and a constant positive potential isimpressed on the screen electrode of |43 through the conductor |23. Thecathode and suppressor electrode of |43 are connected to ground throughresistance |48 to provide self-bias for the control electrode. Anodevoltage is supplied through conductor |20 and the inductance |44.

The output voltage of |43 is fed through condenser |41 to the controlelectrode of |48. A constant potential ig provided on the screenelectrode of |48 through conductor |22 and the cathode of |43 isconnected to ground through the resi-stance |48a to provide self-biasfor the control grid of |43. Plate voltage is supplied to |43 throughconductor |2| and the tuned transformer primary I50a.

The output of the amplifier is rectified by the rectifier |54 and isimpressed upon condenser |55 through the resistance |58 to charge thecondenser. The resistances |58 and |59 are of such value as to give thecondenser resistance network a time constant considerably lower than theslowest rotation of the member I8'. By the conductor ISI there .isprovided a control bias to regulate the gain of the amplifier in themanner of an automatic volume control circuit to compensate forfluctuation in the light-transmission factor of the liquid beingmetered. The potential on the control grids of |88 and |81 is suppliedrespectively from successive half-waves of the alternating current byresistances I 84 and |85 from condenser and through condensers |1| and|12 from transformer secondary |5017. The potential from condenser |55is a negative potential which is self-regulating in magnitude tocompensate for the varying strength of the signal from the transformersecondary |5017. Thus, as the fluctuating light flux that falls on theentrance window of |3' is modulated by the mem'- ber I6', the tetrodes|88 and |81 become alternately conducting and non-conducting as thealternating current potential from the transformer secondary |5011becomes greater or less than average potential on condenser |55.

With the blade |33a in circuit-open position and the blade |34a inposition to close-circuit the conductors |84 and |8317 and the switch|33e closed, the midpoint potential of the transformer secondary |33b isimpressed on the control electrodes of the tetrodes 203 and 204.` Thispotential fiuctuates between two values, one of which is more positivethan the other, thereby rendering the tetrodes 203 and 204 alternatelyconclue tive and non-conductive. Upon the tetrodes 203 and 204 becomingconductive, current flows through the transformer secondary 20012 toprovide impulses for actuating the counter, such impulses being in oneto one ratio with the half revolutions of the rotor I8.

The rotary switches in combination with the tetrodes 2|2 and 2I3 providemeans for securing an adjustable ratio between the number of halfrevolutions of the member I5 and the number of counter-actuatingimpulses. Such means is rendered operative by opening the switch |33eand by moving the blade |3311 into circuit-closing position, therebysimultaneously moving the blade |84a into position to close the circuitfrom |84 to |88. g

Power from transformer secondary |881 controlled by the tetrodes |88 and|81 is fed through the conductor |84 to the operating coil |88 oi' thetwo-bank rotary switch and the wipers |88 and |88 are advanced one stepfor each current impulse in the well-known manner. In order to providean adjustable ratio between the revolutions of the member I8' and thenumber shown on the counter, the connections shown on the drawings areprovided. The wiper |88 can ground either conductor |11 or |18 andcontacts |88 connected thereto as the wiper moves over successivecontacts |81 while the wiper |88 can connect either conductor to thecontrol electrodes of gas-filled tetrodes 208 and'284. Thus, if wipers|88 and |88 are both connected to the same group oi' contacts |88, thenthe tetrodes 208 and 284 will conduct respectively forvsuccessivehalfwaves of the alternating current. If, however, the wipers |88 and|88 are not connected to the same group of contacts |88, negativepotential from |83 to the' control electrodes will cause the tetrodes208 and 284 to become non-conductive respectively i'or successivehalf-waves of the alternating current. Thus, if either wiper |88 or |88moves from connection with one group of contacts |88 to connection withthe other group of contacts and then back to connection with the firstgroup, it will cause the addition of one digit on the counter 228. I'hewiper |88 by engagement with the grounded contacts |81 causes energizingcurrent to ilow through the coil |88 thereby moving wiper |88 ahead onecontact on bank |81 through operation of the tetrodes 2|2 and 2 i8 forevery fty contacts which switch |85 cell is varied in timed relation tothe rotational makes. The connections of the contacts as shown y in Fig.4 provide a ratio between each half revolution of the member |6' and theactuating impui-ses of the counter so that the counter will be advancedcorresponding to the half turns of the member I8 if the coil 228 isconnected directly. to the resistance 22|.

In the event that the metering device is being used for liquid such asmilk or cream, the density of which remains substantially constant overa wide range of temperatures, the blade of the switch 222 is engagedwithithe contact 224 so that impulses from the transformer secondary28817 are supplied directly to the coil 228 of the counter. However, inthe event that the liquid being metered is gasoline or the like in whicha change of density results from a slight change in temperature, theblade oi the switch 2221s engaged with the contact 223 so that theimpulses from the transformer secondary 20Gb are supplied to the wiper228 of the rotary switch and to its stepping mechanism. The number ofimpulses transmitted to the counter depend upon the position of thewiper 235 which in turn depends upon the temperature of the liquid beingmetered. With the liquid at one temperature, the wiper 285 engages allthe auxiliary contacts 234 so that all the impulses from the transformersecondary 228D are supplied from the switch contacts, panel contacts andauxiliary contacts to the coil 228. However, with the liquid at a highertemperature with a resulting .decrease in the density of the liquid, thethermostat 231 is operated to disengage the wiper 235 from one or moreof the aux-- illary contacts, thereby correspondingly reducing thenumber of `impulses which aretransmitted giz'cm the transformersecondary 2201) to the coil speed of the member. I8' and the ysamecircuit arrangements can be used to actuate the counting means as abovedescribed. If desired, a synchronous motor may be -used as thecounteractuating means.

In the embodiment of Fig. 5, the tube 24' and the amplifying systemconsisting of the electron discharge devices |4|, |43 and |48 arereplaced by a multiplier phototube 248 having a lightresponsive element,such last-named tube being a commercial product put out by RadioCorporation of America. Light from the tube i3 is directed to thephoto-cathode 24| which is connected to one terminal of a transformersecondary 242b and the anode 243 is connected to the remaining terminalof 24212 through the tuned circuit consisting of |58a and |5l. Power issupplied to 24| through the transformer primary 242a and the dynodes ofthe tube 248 are connected to intermediate points of 242b. The output of24| corresponds to the output of |48 in Figs. 6 and '7.

Furthermore, it is to be understood that-various modifications may bemade in the abovedescribed device without in any way departing from thespirit ofthe invention as defined in the appended claims.

This application is a continuation-in-part of applicants- .co-pendingapplication, Ser. No. 363,238, illed October 29, 1940,l Meteringdevices.

I claim:

v1. In combination, a conduit, means controlled by ilow of materialthrough said conduit for producing electrical impulses, a step by stepswitch having a plurality of contacts and a movable wiper, means forimposing said electrical impulses on said wiper, counting meansactuatable by electrical impulses, means electrically connecting certainswitch contacts to said counting means, and means responsiveto thetemperature of the material in the conduit for selectively connectingthe remaining switch contacts tosaid counting means.

2. In combination, a photo-electric cell, means to illuminate saidphoto-electric cell at predetermined frequency,'means to vary theintensity of illumination of said photo-electric cell independently ofthe frequency of illumination to -cause said photo-electric ce11 toproduce an output voltage'having an alternating current comcontrolelectrode, means for impressing alternating current output potentialfrom said amplifier on the input of said tetrode periodically to revducethe negative bias of the tetrode control electrode, an electrondischarge relay, and means for impressing the output of said tetrode onthe input of said relay to control the latter. i

3. In combination, a photo-electric cell, means to illuminate saidphoto-electric cell at predetermined rrequency,means to vary theintensity ofillumination of said photo-electric cell independently ofthe frequencybf'illumination to cause said photo-electric cell toproduce an output voltage having an alternating current component, anamplifier, means for impressing the alternating current output voltageof the photoelectric cell upon the input of said amplifier, a rectifier,means for impressing the output voltage of said amplifier on the inputof said rectifier, a tetrode, means for impressing direct currentvoltage from the output of said rectifier on the input of said tetrodeto bias negatively the tetrode control electrode, means for impressingalternating current output potential from said amplifier on the input ofsaid tetrode periodically to reduce the negative bias of the tetrodecontrol electrode, a step by step switch, operating means thereforcontrolled by the output of said tetrode, two conductors connectedto thecontacts of said switch dividing said contacts into alternate groups, anelectron discharge relay having a control electrode connected to thewiper of said switch, means for intermittently grounding said switchcontacts, and means normally applying negative potential to said controlelectrode.

4. In combination, aphoto-electric cell, means to illuminate saidphoto-electric cell at predetermined frequency, means to vary theintensity of illumination of said photo-electric cell independently ofthe frequency of illumination to cause said photo-electric cell toproduce an output voltage having an alternating current component, anamplifier, means for impressing the alternating current ouput voltage ofthe photoelectric cell upon the input of said amplifier, a

' rectiiier', means for impressing the output voltage of said amplifieron the inputof said rectifier, a tetrode, means for impressing directcurrent voltage from the output of said rectifier on the input of saidtetrode to bias negatively the tetrode control electrode, means forimpressing alternating current output potential from said amplifier onthe input of said tetrode periodically to reduce the negative bias ofthe tetrode control electrode. a step by step switch having a pluralityof contacts and a movable wiper. operating means for -said wipercontrolled by the output of said tetrode, a rst and a second conductorconnected alternately to groups of successive contacts, an electrondischarge relay, means electrically connecting said wiper to the controlelectrode of said relay, means for impressing negative potential on thecontrol electrode of said relay, and means for intermittently groundingsaid groups of contacts individually.

5. In combination, a photo-electric cell, means to illuminate saidphoto-electric cell at predetermined frequency, means to vary theintensity of illumination of said photo-electric cell independently ofthe frequency of illumination to cause said photo-electric cell toproduce an output voltage having an alternating current component, anamplifier. means for impressing the 12 alternating current outputvoltage of the phltoelectric cell upon the input of said amplifier, arectifier, means for impressing the output voltage of said amplifier onthe input of said rectifier, a

tetrode, means for impressing direct current voltage from the output oisaid rectifier on the input of said tetrode to bias negatively thetetrode control electrode, means for impressing alternating currentoutput potential from said amplifier on the input of said tetrodeperiodically to reduce the negative bias of the tetrode controlelectrode, a first step by step switch having a first and a second setof contacts and a movable wiper for each set. actuating means for saidwipers controlled by the output of said tetrode, a-first and a secondconductor connected alternately to successive contacts of said firstgroup. means grounding a contact of said second set, a second step bystep switch having a plurality of contacts and a movable wiper,actuating means for said second switch wiper operable upon engagement ofthe second wiper of the first switch with the grounded contact of saidsecond set of the first switch contacts, means connecting said iirst andsecond conductors with selected contacts of said second switch, a secondtetrode having its control. electrode connected to the second wiperof--the first switch and its output circuit connected tothe operatingmeans for the second switch, an electron discharge relay, meanselectrically connecting the first wiper of the first switch to thecontrol electrode of said relay. and means for impressing negativepotential on the control electrode of said relay.

6. In combination, a photo-electric cell, means to illuminate saidphoto-electric cell at predetermined frequency, means to vary theintensity of illumination of said photo-electric cell independently ofthe frequency of illumination to cause said photo-electric cell toproduce an output voltage having an alternating current component,

an amplifier, means for impressing the alternating current outputvoltage of the photo-electric cell upon the input of said amplifier, arectifier, means for impressing the output voltage of said amplifier onthe input of said rectifier, a tetrode, means for impressing directlcurrent voltage from the output of said rectifier on the input of saidtetrode to bias negatively the tetrode control electrode, means forimpressing alternating current output potential from said amplifier onthe input of said tetrode periodically to reduce the negative bias ofthe tetrode control electrode, an electron discharge relay controlled bythe output of said tetrode, a step byl step switch having a plurality ofcontacts and a movable wiper, means controlled by said relays forsupplying current impulses to said wiper, a counter. electro-magneticactuating means therefor, means electrically connecting selected switchcontacts to said actuating means, and temperature-responsive means forselectively connecting the remaining switch contacts to said actuatingmeans.

